1,2-Hydrogen shifts in [W(eta -C5H5)(2)(CH3)](+) have been shown to proceed
via a hydridocarbene intermediate and an agostic methyl complex. The energ
y difference between the two is estimated as 42 kJ mol(-1) with the hydrido
carbene being the more stable. Calculations on the two phosphine adducts [W
(eta -C5H5)(2)(H)(CH2PH3)](+) and [W(eta -C5H5)(2)(CH3)(PH3)](+) confirm th
e latter to be the thermodynamic product of the reaction.